Soil rippers and related devices have found application in a number of areas. They are commonly used on construction sites for fracturing subsoils, particularly when these are underlaid by hardpans or are rocky. Rippers also find wide agricultural use where they are likewise employed for breaking up hardpan or other types of impermeable subsoils. Cable plows are a modified type of ripper which simultaneously create a deep, narrow trench and bury an electrical or other type of cable within the trench.
Agricultural ripping usually has a two-fold purpose in that it fractures subsoils to make them permeable to both plant roots and water. When these impermeable formations are close to the surface; the soil may be poorly drained yet have a tendency to dry out rapidly under droughty conditions. Fracturing of these impermeable soils by ripping creates an environment which can be more easily penetrated by roots. The rip lines themselves tend to act as moisture reservoirs.
One large-scale application of ripping is in reforestation of logged or otherwise unproductive forest lands. There is much land in the southeast and the southern part of mid-continent America in which forest soils are underlaid by shales or hardpans which lie close to the surface. Tree growth on such lands is less than optimum from the standpoints of both size and rate, even though other aspects of the environment are favorable. It has become a standard silvicultural practice in many areas to rip the sites before they are replanted with tree seedlings. Commonly, the seedlings will be planted directly in rip lines, which are located on a spacing considered optimum from the silvicultural standpoint. Depending on the nature of the soil and subsoil, the rips may be anywhere from 40 cm to 1 m in depth, or even greater.
Because of the strength of the substrate and the considerable depths to which it is being fractured, ripping is normally carried out using large tracked, crawler-type prime movers. The land itself is often rough and uneven and is typically covered with logging debris and stumps. All of these considerations work together to virtually exclude the use of smaller, lower powered prime movers.
A typical ripper comprises a frame carrying a tool bar, one or more ripping teeth mounted on the tool bar, and an actuating mechanism. This is rigidly bolted behind a crawler-type tractor. Most typically, because of the high amount of power required, not more than two ripper teeth will be used. The mechanisms used to control the position and attitude of the teeth are well known. These usully have either a radial-arm type control linkage or a parallel-arm type, with the latter type prevailing. Hybrid types are also reasonably common. These may be made with either compound radial linkages between the control mechanism and the ripper teeth, or a combination parallel-radial linkage. Examples of these types can be seen in the following patents.
Larson, U.S. Pat. No. 3,503,546 shows a hybrid linkage in which a lower cylinder serves to actuate a parallel-arm motion and an upper cylinder can be used to give a radial arm action. The two cylinders, which may be operated simultaneously, produce a form of motion on the ripper tooth which will be intermediate between the two types.
Mayo, et al, U.S. Pat. No. 3,295,612 shows a modified parallel-arm linkage, which, in effect, gives an arcuate entry of the tool into the ground, similar to a radial type.
The major difference between the parallel arm and the radial arm control linkages is in the mode of entry of the ripper tooth into the ground. The parallel arm control linkage causes essentially a straight line insertion of the tool into the ground in the same attitude it will have during operation. In radial-arm linkage, the tool tip describes a wide arc as it enters the ground. This type generally requires more power on entry because the ripper tooth typically has a less favorable angle and must sweep through the ground to assume an operating attitude. This deficiency is one of the reasons for the present higher popularity of parallel-arm type rippers.
One problem encountered in using rippers on debris-covered land is that they tend to act as rakes. Accumulated debris periodically will be discharged by withdrawing the teeth from the ground. Frequently the tractor operator must resort to maneuvers such as reversing his machine to clear this accumulated debris. In this regard, a radial arm action has an advantage over the parallel arm action in that it will clear debris more rapidly. This is a problem of no small consequence in ripping logged over forest land. It is common for the ripper operator to spend about 25% of his time in the field clearing accumulated debris. This wasted time is expensive because of the high capital cost of the prime mover and also because of the large amount of fuel and operator time that is used unproductively. Conventional rippers present other problems as well. Because they are located behind the prime mover, they tend to act as a rudder, which interferes with steering. When the tractor operator must make a sharp turn while ripping, he must overcome not only the forward resistance to the ripper teeth, but the newly introduced lateral component as well. Furthermore, as the prime mover rides over objects such as a stump or a log, there is a significant pitching action that is magnified by the distance between the tractor center of mass and the ripper teeth. At one point, this drives the ripper teeth much deeper than required into the ground, thus requiring substantially more power. At another point in travel the ripper teeth may be lifted completely from the ground, thus failing to do the job for which they are intended. The net result is an undesirable undulating rip depth.
The present invention has been successful in overcoming these problems by side mounting the rippers on a crawler-type prime mover approximately opposite the fore/aft center of mass.
While side mounted rippers have been proposed previously, they have never been made available commercially. Perhaps one reason is that they have not successfully addressed a major problem of resisting lateral thrust forces that act on the ripper teeth during operation. One instance in which these forces are very high is when a tooth tries to deflect around the edge of a large subterranean boulder. Ripper mechanisms that are not substantially mounted can literally be twisted off the vehicle.
One side-mounted ripping device known to Applicant is shown in Stedman et al., U.S. Pat. No. 4,152,991. This is a ballast ripper designed for breaking up compacted railroad bedding. It consists of two vertical shafts and appropriate bearings, with horizontal ripper elements working arcuately beneath the railroad ties. Both the prime mover and the ripper mechanism are significantly different from those in the present invention. It is hard to visualize the Stedman machine being useful for anything beyond the specific application for which it was designed.
U.S. Pat. No. 4,204,578, also to Stedman, shows a side-located ripper mechanism having a hybrid-type action. The ripper teeth and actuating means are mounted on "wing portions" comprising buttressed vertical faces welded on the outside of a U-shaped frame. This frame is located in the position normally occupied by a blade arm and blades.
McCauley, in U.S. Pat. No. 2,396,739, shows a bulldozer equipped with ripper teeth that function when the tractor moves backwards. Two of the teeth are mounted on the outside of the blade arms, immediately behind the blade.
U.S. Pat. Nos. 2,358,298, 2,737,868, 3,046,917, 3,092,187, and 3,387,665 all show side-mounted cultivators on light agricultural tractors. The patent to Rafferty, U.S. Pat. No. 2,743,655, shows mid-mounted plows which are essentially in line with the rear wheels of the vehicle.
Most of these devices are either light duty implements designed for tilling or cultivating surficial soil, or would not be suitable for subsoil ripping in many soils because of the side thrust problem.